Abstract: A system for reproducibly measuring motion along surfaces of arbitrary or indeterminate length and of arbitrary curvature, using an opto-electronic sensor mounted to an object in motion along the surfaces. The system involves the detection of alternating reflective and non-reflective markings, on surfaces which can be curved in a certain dimension and can be of any length. Additionally, the system can be applied to measure the motion of camera carts or dollies along straight track, curved track, or any combination of straight and curved track.